Electrical measuring instrument.



e. CAMPOS.

ELECTRICAL MEASURING INSTRUMENT.

APPLICATION HLEDOCT. 10. 1913.

1 2L996. Patented 000111916.

Fig.1 6 5 9 Low Tension High fension a g 10 E5 2) LT I I i Fig. 2 5 L 59 L tension High Tension 0 0000 v in 10 2E 3 E 5 Q i 'Vl/J; Z 4/1 2';5e; E

UNITED STATES PATENT OFFICE.

GINO GAMPOS, 0F MILAN, ITALY.

ELECTRICAL MEASURING INSTRUMENT.

Specification of Letters Patent.

Patented Oct. 17, 1916.

Application filed October 10, 1913. Serial No. 794,438.

To all 'whom it mag concern:

Be it known that I, GINO Campos, a sub into. This result is obtained byan arrange- I ment which permits the addition to the power, at the pointof introduction, of all of the lossesbetween that point and the pointonthe high tension side at which the power is to be ascertained, orwhich permits, instead, the subtraction of the losses occurring betweenthe aforesaid point of introduction and a predetermined point on thelow-tension side. The arrangement in question comprehends a wattmeter,or thelike, in

which there are employed, in addition to the usual windings, a specialwinding designed to give a couple proportional to the square of thecurrent intensity, and a second special winding designed to give acouple proportional to the square 'of the voltage. These two couplesmust be suitably-proportioned, and their action must, either be addedto, or. subtracted from, the ordinary action of the wattmeter.

In the accompanying drawing, Figure 1 indicates diagrammatically atriphase-hightension line, and" Fig. 2 indicates diagrammatically amonoph'ase line. I

Referring to Fig. 1', the triphase, hightension line 1 1, 1' feeds thetriphase transformer 2 and through the latter the lowtension line 3,3,3. Let it be supposed that the power is 'to be measured at the points4,4, 4 on the high-tension side, and that for certain reasons it ispreferable to introduce the instrument on the low-tension side, that isto say, after the transformer.

In applying the present invention to the particular 'case underconsideration, it is proposed to utilize, on the low-tension side, a,wattmeter whichis so constructed that it will indic'atetheelectricalpower, as well as the losses in the transformer 2, with sufficientexactness in view of the ordinarily slight extent of these losses. Itmay here be stated that the aforesaid losses are of two kinds; one, thelosses in the copper, which can be considered as proportional to thesquare of the secondary current intensity; and the other, the losses inthe iron, ap-

proximately proportional, to the square of the secondary voltage, owingto the slight variations to which the voltage itself is normallysubjected.

If, then:

WVh=the high tension power.-

WVZ =the low-tension power.

Wt =the total losses in the transformer 2. VVi =the loss in the iron.

c-=the loss in the copper.

V :one of the secondary voltage components. I :one of the secondarycurrent intensities.

7" and lc ztwo suitable constants.

And if it be assumed that the losses in the transformer constitute abalanced load, it follows that:

Then, by substitution,

Wh=WZ+Ic'V +Zc I The last'equation shows that it is possible to measure.the power Wk on the high-tension side by means of an instrument capableof adding to the measure of the power WZ on the low-tension side anamount proportional to the square of the secondary voltage, and a secondamount proportional to the square of the secondary current intensity.In, fact, there canfbe employed for this purpose, as in Fig. 1, a doublewattmeter constructed in accordance with the present invention, and inthe partlcular case under consideration, one of the two current coilshad involved a monophase line, (Fig. 2), or

a triphase balanced load, with the measuring instrument introduced onthe low-tension side, as before, there could be employed, instead of adouble wattmeter, a single wattmeter with two supplemental coils, i. e.,.a movable current coil 10 and a fixed tension coil 9, in addition tothe ordinary fixed current coil 5 and movable tension coil 6. Suchappliance does not consist merely of a wattmeter and twoelectrodynamometers but includes in addition a second wattmeter whichlatter isproduced by the mutual action of the two supplemental coils;this second wattmeter, however, if properly constructed, will not set upany harmful action, but will simply modify the constant of the principalwattmeter. In like manner, as there are induction wattmeters forbalanced or unbalanced alternating circuits, and induction voltmetersand ammeters able to give a torque more or less proportional to thesquare of the pressure, or current, all such instruments having fixedcoils acting on a movable disk or cylinder, the present invention can beapplied to them; in such a case a wattmeter, a voltmeter and an ammeterof the induction type would be employed, acting on the same axis so asto obtain a compensated wattmeter.

As regards the electrodynamical instruments, some parts may be dispensedwith, using for the voltmeter and ammeter the movable element of thewattmeter and even its fixed coils or some of them and adding only suchcoils as are necessary. Furthermore, thevarious parts may be providedwith special additional accessories, or they may be suitably divided, inorder to control their action. For instance, when a plurality oftransformers is included in the circuit, only certain ones of which areactually working, the arrangement can be such that the supplementalcoils will act only with relation to the aforesaid working transformers.Instead of being inserted directly in the line, the wattmeter and itssupplemental parts may be fed by either Voltage or current transformers.

The compensations which have been considered with relation to the lossesin the iron and in the copper, may be referred to with relation todifferent factors or quantities, for instance, losses of power in adistribution line. In this case, in an overhead line, the losses will beproportional to the square of the current, the resistance beingconsidered as constant, while in the case of cables, the'losses in thedielectric can readily be determined, since they'vary in accordance withthe square of the tension. Likewise, in overhead lines of extra hightension, compensation can be made for corona losses, which depend uponthe tension of the current and can be considered as proportional to thesquare of the tension. Compensations for losses arising from differentcauses may even be accumulated when they depend upon the same factor orquantity, voltage or tension. Thus, compensations for losses in a doubletransformer and in an intermediate line between two transformers may bejoined together. Accordingly, it would be possible, in the case of alowtension generating station which feeds a low-tension receivingstation, even through the intermediary of a high-tension transmissionline and two transformers, to measure the power at one of the twostations by introducing an instrument at the other station, or even uponthe high-tension line.

In general, it is possible to even compensate for mechanicaltransformations corresponding to losses of power of which the instrumentmay take account, and the readings or indications given can be changedin accordance with the tension or the voltage, or with other quantitiesassociated with the same.

The instrument, instead of being an indi cating or recording wattmetercan also be an integrating wattmeter (watt-hour meter) or other similarappliance acting under the ings, one movable and the other fixed,producing variations in the wattmeter'measurements, the first-namedsupplemental winding giving, by the action of the fixed prin cipalwinding upon it, variations proportional to the square of the currentintensity, while the other supplemental winding gives, by the action ofthe movable principal winding, variations proportional to the square ofthe voltage.

In testimony whereof I afiix my signature.

GINO CAMPOS.

